Trachoma, caused by an ocular infection with C. trachomatis is the leading infectious cause of blindness worldwide. A number of epidemiologic studies of trachoma done by the investigators have elucidated the populations at risk for blinding sequelae of trachoma, and these studies suggest a number of potentially effective control strategies. This project would develop and test an epidemiologic model for trachoma which would consist of a transmission model for active disease, and a progression model for blinding sequela. We are proposing to model the non-homogeneous mixing of trachoma in a hyperendemic area by stratifying risk groups according to age, sex and household characteristics. The model will integrate current knowledge on chlamydial infection, transmission, disease, and blinding sequelae. Data for this model are available from the investigators unique, longitudinal series of data sets from trachoma hyperendemic areas of Tanzania and Oman. Development of such a model offers a powerful method for testing alternative control strategies in resource poor areas where time and cost constraints may limit field studies. Such strategies include programs to change hygiene behavior, mass antibiotic treatment, and surgical intervention for trichiasis/entropion. Data from this model will be critical for decision making on direction for trachoma control for the future.